Call audio gets muffled through the plastic and it looks dumb holding a pouch to your ear. Fine for keeping it dry, but annoying if you take a lot of calls.
You’re right to be skeptical, paint doesn’t fix moisture. Anti-mold paints or additives can slow visible regrowth after you clean the spot, but they aren’t a long-term cure. For a tiny damp corner I usually just clean it, treat the mold, repaint and live with it until the wall needs proper repair.
You’re probably overestimating how much it’s actually waking her, I think cats tune out repetitive sounds. Maybe she just shifts and the bell is noticeable to you, not a full wake-up. Not totally sure, but I wouldn’t lose sleep over it unless you see full nights of restlessness.